The field of the invention is imaging techniques for use with projected moving images for the reduction or elimination of geometric distortion. The technique is particularly useful in motion pictures, amusement rides, and the like.
Since the inception of motion pictures, the ability to present realistic sequences of moving images has been particularly desirable. The methods and techniques of projecting a series of images onto a screen are now well understood whether from photographic film, video output, or output from a computer. While the projection techniques used in modem motion pictures are capable of producing realistic visual effects, there remains numerous factors that limit the perceived realism or fidelity of the images. Some of the more important limitations include brightness, color, accuracy, sharpness, strobing, aliasing, artifacts, and grain. One particularly troublesome limitation on the realism and fidelity of moving projected images is geometric distortion.
Geometric distortion of the projected image can result from any one of many factors. For example, some of the more important factors of geometric distortion are: (1) the refractive properties of the original lens through which the images were captured or created, (2) the refractive properties of the projector lens, (3) the location and orientation of the projection screen relative to the projector, and (4) the location of the viewer relative to the projection surface.
The first three factors mentioned above have generally been carefully fine-tuned since the inception of motion pictures so as to produce the most convincing illusion of reality for the viewer. For example, camera lenses and projector lenses are carefully designed and selected so as to produce the least distortion possible. Moreover, the orientation of the projection screen and the projector are positioned so as to optimize the illusion of reality of the image.
The last factor, namely the orientation of the viewer relative to the projection screen has been particularly problematic. For example, in a typical motion picture theater, point of view distortion can be readily observed. If a viewer sits near the center of the theater, the moving images appear xe2x80x9ccorrectxe2x80x9d in that the moving images appear as they would in real life. However, as the viewer moves nearer the projection screen, or moves to the right or left of center, the apparent shape of the projection screen changes. This shape of the projection screen appears to be foreshortened, i.e., the shape changes to appear as a rhombus. (See FIG. 3). As a result of the foreshortening, the images look distorted to the viewer, and the perceived quality of the images suffers.
Image distortion is particularly noticeable when viewing 3D or stereoscopic motion pictures. Stereoscopic motion pictures have always been produced for a stationary audience, typically using xe2x80x9c3Dxe2x80x9d eyeglasses or visors. The viewpoint of the viewer or audience does not move relative to the image projection surface or screen. However, if the viewer moves relative to the projection surface, the perspective shift unnaturally and appear to xe2x80x9cfollowxe2x80x9d the viewer around the room. Up until now this xe2x80x9cfollowingxe2x80x9d effect has not created any drawbacks in 3D theatres, as the audience in such theatres has always been seated in a fixed position relative to the screen. However, in contrast to known 3D theatres, the invention combines 3D images with movement of the audience, to produce a thrilling and novel combination of visual and sensory effects. As a result, the xe2x80x9cfollowingxe2x80x9d effect must be accounted for.
As an example of the xe2x80x9cfollowing effectxe2x80x9d, if a stereoscopic image on the screen was recorded by a camera located at an intersection looking down a corridor of tall buildings, and if the viewer started walking around in the theater, the entire scene would seem to revolve and rotate as seen from the viewer""s perspective. No matter where the viewer walks in relation to the projected image, the image will move, rotate, contract, and stretch, so that the viewer perceives he or she is standing still in the same location. This characteristic provides an environment to the viewer that is completely unrealistic, and greatly diminishes the realistic impression given to viewers that are in motion relative to the screen or projection surface.
Consequently, with the combination of 3D images and movement of the audience provided by the invention, there is a need for a method of compensating for the point of view distortion that takes place when a viewer moves relative to a projected stereoscopic 3D image, and to eliminate the following effect occurring in traditional stereoscopic 3D projections. There is also a need for the projected images to look as realistic as possible, giving the viewer the impression that he or she is looking through a xe2x80x9cwindowxe2x80x9d into a virtual world.
The present invention is directed to an image correction method to compensate for point of view image distortion.
In a first separate aspect of the present invention a method for compensating for motionless point of view image distortion is provided. The method includes the steps of obtaining an image within a predetermined frame at a first position, the image comprising an array of image points, wherein at the first position, the image is distorted due to point of view image distortion. The distorted image is then transformed into a compensated image, the transformation comprising the step of re-mapping the array of image points of the distorted image using a transformation function. The transformation operates on the array of image points to stretch the distorted image to fill the entire frame. The compensated image is projected at a second position different from the first position, such that the projection of the compensated image substantially reduces point of view image distortion at the first position.
In a second separate aspect of the present invention, a method is provided for compensating for point of view image distortion for a moving point of view. The method includes the steps of first determining a motion profile of the moving point of view. A frame of view is then established onto which an image is projected. The temporal and spatial relationship between the moving point of view and the frame of view is determined at each point along the moving point of view. A plurality of images of the frame of view are obtained from a perspective of a moving point of view while traveling through the motion profile, the plurality of images comprising an array of image points of the frame of view. Each of the plurality of images are then transformed into a plurality of compensated images, the transformation comprising the steps of re-mapping the array of image points of the frame using a transformation function. The transformation function fits each of the plurality of compensated images into the size of the frame of view from a stationary perspective point. The compensated images are projected onto a projection surface from the stationary perspective point in synchronization with the moving profile to substantially reduce point of view image distortion.
Accordingly, it is an object of the present invention to provide a method of compensating for point of view image distortion. Other and further objects and advantages will appear hereafter.